For many years load demand control systems have been in use; however, with the recent increase in the cost of electrical power, load demand control systems are becoming more of a necessity for installations wherein a number of electrical loads are used. It is possible to shed certain electrical loads during certain periods of time to maintain the average electrical load input to the installation below some predetermined value. Specifically, a conventional demand control system senses the incoming power to an installation and controls the number of operating loads to maintain the incoming power below some predetermined value. If a particular load is to be operated and has priority over the other loads, upon the operation of the priority load, the demand control system would turn off or shed other loads which have a lower priority to maintain the incoming power demand within certain limits.
As most electric utility companies charge commercial users for the total kilowatt hours of electrical energy used in a given period, such as each month at a rate depending upon the peak kilowatts of power averaged over any short interval of time, such as fifteen minutes, during any time each month, it is important to reduce short peak loads.
When a commercial user or an installation has a large electrical load that must be periodically energized, it is not always possible to shed other loads to the extent necessary to keep the total kilowatt energy use for any interval as low as desired. There is an incentive for a commercial user to anticipate the operation of large loads and reduce the electrical load peaks which extend over portions of a preselected time interval.